A shadow looks like a copy, but it changes dramatically when the light, object or surface moves. In this investigation, children make one change at a time and use evidence to explain why a wooden rabbit can cast a tiny shadow, a giant shadow or one that points in a new direction.
Materials
- A flashlight with a cool LED beam
- An opaque toy with a clear outline
- A pale wall or large sheet of paper
- Books or boxes to hold the toy and flashlight
- Painter’s tape, pencil and ruler
- Optional chalk and a sunny outdoor space
Check that the flashlight does not become hot. Keep button batteries locked inside the device and out of children’s reach; swallowed batteries are a medical emergency.
Set up the indoor laboratory
Dim the room without making it unsafe to move around. Put the toy about 30 centimetres from the wall and the flashlight behind it. Make a shadow. Ask the child to name the three necessary parts: light source, object blocking light and surface receiving the shadow.
Experiment one: change light distance
- Mark the starting positions of flashlight and toy with tape.
- Trace or measure the shadow’s height.
- Predict what will happen if the flashlight moves closer to the toy.
- Move only the flashlight; keep toy and wall fixed. Measure again.
- Move the flashlight farther away and compare.
Describe what happened before explaining it. The closer light spreads around the object at wider angles, often producing a larger shadow on the wall.
Experiment two: change direction
- Return everything to the start marks.
- Predict where the shadow will move if the flashlight shifts left.
- Move it left, then right, then higher, one position at a time.
- Draw arrows showing the light’s position and the shadow’s direction.
NASA’s Bear’s Shadow activity similarly invites families to move a flashlight around an object and observe the resulting shadows.
Experiment three: make two shadows
With adult help, add a second flashlight from another direction. Predict how many shadows appear and which belongs to each light. Turn one light off to check. This is a useful reminder that a shadow is caused by blocked light, not a dark substance attached to the toy.
Optional outdoor shadow tracker
On a dry day, trace the shadow of a fixed pole or mark the tip of a child’s shadow in the morning, around midday and later afternoon. Keep the object in the same place. Record time and weather. Never look directly at the Sun, even through sunglasses, a camera or binoculars. Use sunscreen, hats and water as appropriate, and avoid extreme heat.
Ask what changed and what stayed fixed. The outdoor pattern relates to the changing position of the Sun in the sky as Earth rotates, but one day’s marks do not explain every seasonal difference.
Variations by age
- Ages 3–5: Make animal shadows and use bigger, smaller, longer and shorter.
- Ages 6–9: Change one variable, trace results and explain the direction opposite the light.
- Ages 10–12: Measure distances and shadow sizes, repeat trials and graph the relationship.
Accessible participation
Mount the flashlight in a clamp or on blocks so a child can direct a partner or use a switch. Use high-contrast objects and a large wall. A child with low vision can feel the toy positions, control the light and record spoken predictions; focus on warmth-free safe equipment and verbal description.
Reflect like a scientist
- Which change made the shadow largest?
- What evidence showed the shadow moved opposite the light?
- What would make this a fairer test?
- What new question should we test?
Extend the idea with rotation and orbit through movement, prediction-based kitchen experiments or measuring and mapping games. Shadows reward careful control: one changed variable can transform the whole picture.
